FlashNeko, you brought up a lot of good points but I still think Decade was not as good as Gokaiger. It only executed some ideas that turned out awesome (a few of the AU worlds, Shinkenger crossover, Black/RX world) and the rest had you scratching your head. I'm still mad at the original ending too. That was not the best way to end a show at all. It felt like a cheap shot in a boxing match, where they give you a punch when you least expect and expect you to chase after them. That's how I felt with Toei's decision to do because they felt you HAD to go watch the movie to see the "real ending." Turned out that they had to revise the original ending just to properly lead into their movie. Not cool and not very smart.
You mentioned about Gokaiger's ending too. You are right that it felt cheap like Decade's. However, the team had already defeated the Zangyack and thus completed their mission. The way how Decade ended, everything wasn't settled yet. Kenzaki wanted to kick Decade's ass. Lol...The Gokaiger leaving away to fight the rest of the Zangyack is just the proper setup for an epilogue adventure so it was more fitting than a cliffhanger ending like in Decade.